Archiving ≠ Compressing

Two Different Jobs

Scenario: You need to email 2,000 log files to a colleague, and they add up to 800MB. You'll do two things: bundle them into one file, and shrink it. Those are separate operations, and mixing them up is a classic beginner confusion.
OperationToolResult
Archive (bundle many → one)tarA .tar file (a "tarball"), same total size
Compress (shrink)gzip, bzip2, xz, zipA smaller file
Analogy: Archiving is putting all your clothes into one suitcase. Compression is vacuum-sealing that suitcase so it takes less space. tar packs the suitcase; gzip vacuum-seals it. Usually you do both - which is why you see .tar.gz.

So a file called backup.tar.gz was tarred (bundled) and then gzipped (compressed). You'll create these constantly for backups, deployments and transfers.